“Scientific Lecture Meeting Preprints 782”, published in October, Showa 53, by Society of Automotive Engineers of Japan, INC., includes an article [45] Combustion Analysis of Gasoline Engines -from the Viewpoint of Intermediate Combustion Product-(pages 353–362). This article says that burning of gasoline-air mixture starts with the generation of active intermediate products or radicals such as CH- and OH-groups, and then successive burning of the active radicals will follow. Further, it suggests that the active radicals in mixture of air and hydrocarbon fuel such as gasoline can reduce the ignition temperature and ignition pressure for the mixture, thereby contributing to the improvement in combustion characteristics of the mixture.
In light of the above, the present invention is proposed to improve the combustion characteristics of the gas mixture in the cylinders of a multicylinder internal combustion engine that consumes a hydrocarbon fuel such as gasoline, or hydrogen fuel.
Regarding prior arts which may be relevant to the present invention, JP-A-H05-157008 and JP-A-2000-282867 teach that:
“A pressure accumulation chamber is designed to communicate with a combustion chamber so that part of combustion (expansion) gas during the explosion (expansion) stroke is stored in the pressure accumulation chamber, and the stored combustion (expansion) gas is discharged into the combustion chamber during the suction stroke or the compression stroke.”
Further, JP-U-H05-83351, JP-A-H05-187326 and JP-A-H09-68109 teach that:
“In a multicylinder internal combustion engine with a plurality of cylinders sharing a crankshaft, part of combustion (expansion) gas in one cylinder undergoing the explosion (expansion) stroke is introduced into another cylinder undergoing the suction stroke or the compression stroke.”
The radicals, generated in burning gas mixture, increase in amount when the combustion temperature rises, but they are turned into stable substances such as carbon monoxide, hydrogen or methane as the combustion temperature drops. Thus, their activity is highly temperature-dependent and degrades with a drop in temperature.
According to the former group of prior arts mentioned above, part of combustion (expansion) gas in the explosion (expansion) stroke is stored in the pressure accumulation chamber, and the stored gas is discharged during the suction stroke or the compression stroke. With this arrangement, the temperature of the combustion (expansion) gas stored in the pressure accumulation chamber drops greatly as the process proceeds from the explosion (expansion) stroke to the suction stroke or compression stroke through the discharge stroke. As a result, most of the radicals contained in the stored combustion (expansion) gas will disappear by turning into unexcited products or stable produces (such as CO, HC, H2 and H2O) Thus, the former group of prior arts can increase the compression pressure and decrease NOx by the effect of EGR, but cannot improve the combustion characteristics of gas mixture by radicals to be generated by combustion.
The latter group of prior arts mentioned above is merely designed to perform recirculation of exhaust gas into the suction stroke for the purposes of reducing NOx by the EGR effect. Specifically, part of exhaust gas is drawn from a cylinder at the substantial end of its explosion (expansion) stroke to be introduced into another cylinder. Since the combustion temperature has been dropped considerably by the end of the explosion (expansion) stroke, most of the radicals in the combustion (expansion) disappear by turning into stable products. Therefore, the introduction of the combustion (expansion) gas into another cylinder cannot improve the combustion characteristics of gas mixture in the cylinder.
The objective of the present invention is to ensure that the combustion characteristics of gas mixture in the cylinders of a multicylinder internal combustion engine is improved by utilizing the radicals generated by combustion in the cylinders.